A kind of low cost 355MPa is hot rolled H-shaped and preparation method thereofTechnical field
The present invention relates to metallurgical technology field more particularly to a kind of low cost 355MPa are hot rolled H-shaped.
Background technique
New national standard GB/T1591-2018 low-alloy high-tensile structural steel comes into effect in March, 2019, wherein the trade markThe upper yield strength of Q355D is greater than 355MPa, and tensile strength range is 470~630MPa, -20 DEG C of low-temperature impact >=34J, and carbon works asMeasure CEV≤0.45.In in former capital's mark GB/T1591-2008 low-alloy high-tensile structural steel, the lower yield strength of trade mark Q345DGreater than 345MPa, tensile strength range is 470~630MPa, -20 DEG C of low-temperature impact >=34J, CEV≤0.45.From changing for standardIt is seen in change, intensity requirement tends to meet European standard, and carbon equivalent is increased slightly.National standard GB1591-2008 low-alloy high-strength knotQ345C in structure steel, the country mostly use the mode of V microalloying to obtain low temperature impact properties for the production of the realization steel grade.
For the status of domestic steel market doldrums, while guaranteeing that product quality meets properties of product, steel are reducedProduction cost be steel mill pursue target.
Summary of the invention
It is hot rolled H-shaped and preparation method thereof the object of the present invention is to provide a kind of low cost 355MPa, only add alloy memberLower-cost ferro-niobium in element, and reduce the manganese content in steel to reach the requirement of low cost low temperature impact property, not only alloyIt is at low cost, and there is the matching of good obdurability.
In order to solve the above technical problems, the present invention adopts the following technical scheme:
A kind of low cost 355MPa is hot rolled H-shaped, the ingredient including following mass percent: C 0.08~0.12%, Si0.20~0.35%, Mn 1.40~1.55%, P≤0.015%, S≤0.015%, Nb 0.040~0.050%, V 0.01~0.02%, remaining is Fe and inevitable impurity.
Further, the ingredient including following mass percent: C 0.09%, Si 0.30%, Mn 1.42%, P0.012%, S 0.009%, Nb 0.045%, V 0.05%, remaining is Fe and inevitable impurity.
Further, the ingredient including following mass percent: C 0.12, Si 0.35, Mn 1.45, P 0.009, S0.008, Nb 0.048, V 0.018, remaining is Fe and inevitable impurity.
A kind of preparation method that low cost is 355MPa hot rolled H-shaped, includes the following steps:
1) smelting condition
Raw materials and alloy material will comply with standard prescribed requirement, molten iron pretreatment, desulfurizing iron processing, it is desirable that and P≤0.120%；
2) converter
Terminal point control target value: C >=0.06%, P < 0.020%, tapping temperature >=1640 DEG C.
3) it refines
White slag operation is refined, whole to carry out blowing Ar operation by refining regulation, the soft blow time is greater than 8 minutes；
4) continuous casting
TL=1518.5 DEG C of liquidus temperature, molten steel overheat: Δ T≤35 DEG C, target Δ T≤30 DEG C, using permanent pulling rateOperation；
5) hot rolling
1150 ± 50 DEG C of start rolling temperature of rolling, after BD cogging, CCS rack is rolled, and finishing temperature before CCS finishing rolling mill≤900℃；
High-pressure water descaling.
Further, 2) in the converter, using silicomanganese and Fe-al-mn Deoxidizing, there is aluminium final deoxidizing, pushing off the slag of tapping.
Further, 3) in the refining, desulfurization, trimming and heating behaviour are carried out according to converter molten steel ingredient and temperatureMake.
Further, 5) in the hot rolling, guarantee steel billet without being sent to steel rolling mill, steel rolling after surface quality and internal soundnessFactory is visually inspected again before slab enters heating furnace, have scab, crackle, the steel billet for sticking up skin are chosen.
Compared with prior art, advantageous effects of the invention:
1. the present invention is designed by using niobium vanadium composite micro-alloying ingredient, reduces manganese content in steel and reach the comprehensive of H profile steelPerformance is closed, smelting cost is considerably reduced, simple production process is conducive to promote.
2. the matched well that the present invention reaches intensity and impact flexibility without control Alt content.
3. the achievable operation of rolling of the present invention is cooled down without control, delivery use is carried out with rolled, steel have goodGood welding performance.
4, the present invention using Hot Metal in Beam Blank production Low Temperature Hot Rolling H profile steel method, H profile steel specification limit be H150*150~Big specification in H1000*300, is produced using inexpensive smelting process, hot rolled H-shaped -20 DEG C of low-temperature impact works of finished product wing plate≥50J。
Detailed description of the invention
The invention will be further described for explanation with reference to the accompanying drawing.
Fig. 1 is hot rolled H-shaped process flow chart.
Specific embodiment
A kind of low cost 355MPa is hot rolled H-shaped, and Composition Control is as follows: C 0.08~0.12%, Si 0.20~0.35%, Mn 1.40~1.55%, P≤0.015%, S≤0.015%, Nb 0.040~0.050%, V 0.01~0.02%, gas is not required in steel, remaining is Fe and inevitable impurity.
Production technology is converter-LF refining-continuous beam blank casting-casting billet surface cleaning-Rolling With Universal Mill H profile steel-aligning.
Carbon equivalent: CEV=C+Mn/6+ (Cr+Mo+V)/5+ (Ni+Cu)/15, CEV≤0.45.
Mechanical property specific requirement is shown in Table 1.
1 mechanical property of table
Specification: the present invention relates to H150-H1000 tunneling boring is hot rolled H-shaped.
Process route
Process for making: blast-melted-molten iron pretreatment-converter top and bottom complex blowing smelting-LF external refining-Hot Metal in Beam Blank connectsCasting.
Steel rolling process: the feeding-dephosphorization of step heating-furnace-high pressure water one time-BD-CCS universal rolling-hot saw takesSample-step cooling bed cooling-aligning-shape, surface quality inspection-sawing-packing-storage, outgoing.
Process flow as shown in Figure 1 is as follows:
1, smelting condition
Raw materials and alloy material will comply with standard prescribed requirement, molten iron pretreatment, desulfurizing iron processing, it is desirable that and P≤0.120%.
2, converter
Terminal point control target value is shown in Table 2.Using silicomanganese and Fe-al-mn Deoxidizing, there is aluminium final deoxidizing, pushing off the slag of tapping.
2 converter terminal of table controls target value
| C% | P% | Tapping temperature DEG C |
| ≥0.06 | < 0.020 | ≥1640 |
3, it refines
White slag operation is refined, whole to carry out blowing Ar operation by refining regulation, the soft blow time is greater than 8 minutes.According to converter steelWater constituent and temperature carry out desulfurization, trimming and warming temperature.Refining is shown in 3 for casting machine component requirements.
3 Q355D of table is refined for casting machine component requirements unit: %
| C | Si | Mn | P | S | Nb | V |
| 0.10 | 0.25 | 1.45 | ≤0.010 | ≤0.010 | 0.045 | 0.015 |
4, continuous casting
TL=1518.5 DEG C of liquidus temperature, molten steel overheat: Δ T≤35 DEG C, target Δ T≤30 DEG C, using permanent pulling rateOperation.
5, hot rolling
5.1 heating furnace
Steel mill guarantees steel billet without being sent to steel rolling mill after surface quality and internal soundness.Steel rolling mill enters heating furnace in slabIt is preceding to be visually inspected again, have scab, crackle, the steel billet for sticking up skin are chosen.1150 ± 50 DEG C of start rolling temperature of rolling, BD coggingAfterwards, CCS rack (universal mill) is rolled, finishing temperature≤900 DEG C before CCS finishing rolling mill；
5.2 carry out high-pressure water descaling.
6, inspection rule
Slab quality: the inspection rule of Q/BG 526-2015 continuous casting special-shaped base is executed.
7, non-metallic inclusion
The non-metallic inclusion grading of steel executes GB/T10561-2005, is shown in Table 4.
4 field trash of table requires rank unit grade
| A | B | C | D | Ds |
| ≤1.5 | ≤1.5 | ≤1.5 | ≤2.0 | ≤2.0 |
Embodiment 1
The chemical component (weight percent %) of steel are as follows: C 0.09, Si 0.30, Mn 1.42, P0.012, S0.009,Nb0.045, V0.05 remaining be Fe and inevitable impurity.Production method successively include 150t converter, external refining, continuous casting,Heating, BD cogging, universal rolling.The parameter of each step are as follows: use 150t converter smelting, converter terminal C 0.13, P 0.020, S0.020 control converter terminal tapping temperature is 1652 DEG C；Match slag charge when external refining and alloy addition includes: that lime 355 is publicJin, 152 kilograms of silicomanganese, 11 kilograms of vanadium nitrogen iron, 49 kilograms of aluminium manganese iron.1519 DEG C of LF temperature in place, LF off normal 1572 DEG C of temperature, addHot time 24min, the LF refining time 40 minutes.Wherein LF molten steel composition (weight percent %) in place is C 0.10, Si0.03, Mn 1.30, P 0.016, S 0.013, Nb 0.012；LF offs normal molten steel composition (weight percent %) as C 0.09, Si0.30, Mn 1.42, P 0.012, S 0.009, Nb 0.045, V 0.05；Soft blow time 15min guarantees that field trash sufficiently floats.1569 DEG C of pouring temperature when continuous casting, 30 DEG C of the continuous casting degree of superheat, average pull rate 0.98m/min.Steel mill guarantees steel billet without surfaceSteel rolling mill is sent to after quality and internal soundness.Slab of the steel rolling mill by shaped blank having a size of 555mm × 440mm is entering heating furnaceIt is preceding to be visually inspected again, have scab, crackle, the steel billet for sticking up skin are chosen.Furnace temp is 1278 DEG C；Heating time 3 is smallWhen, interior soaking 48min heating furnace is weak reducing atmosphere, and steel billet enters the dephosphorization of roughing mill advance horizontal high voltage water and (enters BD1 machineBefore frame), 1228 DEG C of start rolling temperature of rolling, 1242 DEG C of soaking section temperature, the first 1217 DEG C of bringing-up section temperature, the second bringing-up section temperature1110 DEG C, 1125 DEG C of cogging temperature before BD1, rolling specs H300 × 300 × 10 × 15,890 DEG C of finishing temperature, temperature on cooling table675℃。
5 mechanical properties value of table
6 field trash of table and tissue
Embodiment 2
The chemical component (weight percent %) of steel are as follows: C 0.12, Si 0.35, Mn 1.45, P0.009, S0.008,Nb0.048, V0.018 remaining be Fe and inevitable impurity.Production method successively includes 150t converter, external refining, companyCasting, heating, BD cogging, universal rolling.The parameter of each step are as follows: use 150t converter smelting, converter terminal C 0.11, P0.009, S 0.007 control converter terminal tapping temperature is 1650 DEG C；Match slag charge when external refining and alloy addition includes: whiteGrey 332 kilograms, 152 kilograms of silicomanganese, 18 kilograms of vanadium iron, 36 kilograms of aluminium manganese iron.1520 DEG C of LF temperature in place, LF off normal temperature 1593DEG C, heating time 24min, the LF refining time 44 minutes.Wherein LF molten steel composition (weight percent %) in place is C 0.12, Si0.35, Mn 1.45, P 0.009, S 0.008, Nb 0.039, V 0.015；LF offs normal molten steel composition (weight percent %) as C0.12, Si 0.35, Mn 1.45, P 0.009, S 0.008, Nb0.048；Soft blow time 15min guarantees that field trash sufficiently floats.1577 DEG C of pouring temperature when continuous casting, 29 DEG C of the continuous casting degree of superheat, average pull rate 1.0m/min.Steel mill guarantees steel billet without surface matterSteel rolling mill is sent to after amount and internal soundness.Slab of the steel rolling mill by shaped blank having a size of 555mm × 440mm is before entering heating furnaceVisually inspected again, have scab, crackle, the steel billet for sticking up skin are chosen.Furnace temp is 1268 DEG C；Heating time 2.75 is smallWhen, interior soaking 50min heating furnace is weak reducing atmosphere, and steel billet enters the dephosphorization of roughing mill advance horizontal high voltage water and (enters BD1 machineBefore frame), 1219 DEG C of start rolling temperature of rolling, 1242 DEG C of soaking section temperature, the first 1230 DEG C of bringing-up section temperature, the second bringing-up section temperature1115 DEG C, 1130 DEG C of cogging temperature before BD1, rolling specs H300 × 300 × 10 × 15,892 DEG C of finishing temperature, temperature on cooling table700℃。
7 mechanical properties value of table
8 field trash of table and tissue
The present invention provides a kind of low cost is hot rolled H-shaped and its production technology, product of the present invention rationally designs ingredient, removesIt adds outside niobium alloy, reduces manganese content, and so that its mechanical property is reached low-temperature impact requirement by optimized production process method, againProduction cost can be reduced with most easy, efficient method production and manufacture.
Embodiment described above is only that preferred embodiment of the invention is described, and is not carried out to the scope of the present inventionIt limits, without departing from the spirit of the design of the present invention, those of ordinary skill in the art make technical solution of the present inventionVarious changes and improvements, should all fall into claims of the present invention determine protection scope in.